Synergistic composition for preparing high concentration fullerene (C60) glass and a method for preparing the glass in bulk monolith

ABSTRACT

The present invention relates to a synergistic composition for preparing high concentration fullerene (C 60 )-glass and a method for preparing glass doped with fullerene (C 60 ) in bulk monolith using the synergistic composition, which may be used as a nonlinear photonic material and more particularly as a nonlinear optical medium and optical limiter.

FIELD OF THE INVENTION

The present invention relates to a synergistic composition for preparinghigh concentration fullerene (C₆₀)-glass and a method for preparingglass doped with fullerene (C₆₀) in bulk monolith using the synergisticcomposition. The glass thus obtained is useful as a nonlinear photonicmaterial and more particularly as a nonlinear optical medium and opticallimiter.

BACKGROUND AND PRIOR ART DESCRIPTION

Fullerenes are a class of closed shell carbon molecules havinginteresting optical and opto-electronic properties. Amongst the varioushomologues of the series which may consist of carbon atoms ranging innumber from 20 to 980 and even more (Science of Fullerene and Carbonnanotudes—M. S. Dresselhaus et al, Academic Press, 1996), the moststable and widely investigated molecules are C₆₀ and C₇₀ fullerenes.Structurally, C₆₀ and C₇₀ have similarity in the sense, they haveextended network of conjugated delocalized pi-electrons which aredistributed over the spherical fullerene surface. These compounds have awide variety of remarkable properties. As in the case with manyconjugated polymers, the electrical conductivity of C₆₀ and C₇₀ can bevaried to make them insulators, semi conducting and even superconducting by controlled n-type doping. Lee W. Tutt (U.S. Pat. No.5,172,278 dated Dec. 15, 1992) have first shown that both C₆₀ and C₇₀fullerene solutions can be used as an optical limiter, transparent tolow intensity light but nearly opaque above a critical intensity. One ofthe major difficulties in using fullerenes for all such applications isthat they are unstable under ambient environmental condition. Oxygen andwater in presence of light are known to react with fullerenes. So, forall practical device applications, it is necessary to encase fullerenein suitable solid host.

N. S. Sariciftci, A. J. Heeger (U.S. Pat. No. 533,183, dated 19 Jul.1994) showed that fullerene C₆₀ and C₇₀ may be made technologicallyuseful as photoconducting film by incorporating them into suitableorganic conducting polymer. For optical and optoelectronic applicationshowever, fullerene, incorporated in suitable glassy hosts, should be themost desired materials.

There are number of reports of carrying out experiment for encasingfullerene C₆₀ and C₇₀ in glassy hosts with limited success. In most ofthese cases, fullerene was tried to incorporate in silica host bysol-gel methods, e.g. methods described by B. R. Mattes, W. Duncan, J.M. Robinson, A. C. Koskelo and S. P. Love in U.S. Pat. No. 5,420,081dated May 30, 1995 and by Sheng Dai, R. N. Compton, J. K. Young and G.Mamantov in J. of Am Cer. Soc. 75 (1992) 2865. In all these cases,preparation of thin films/plates of dimensions not larger than 13-15mm×0.5 mm having clusters of C₆₀ or C₇₀ fullerene dispersed in the host,were reported. In some cases, certain derivatives of fullerene were usedto prepare silica-C₆₀ fullerene composite by sol gel method (R.Signorini et at SPIE vol. 2854, page 130). In all these above mentionedcomposites, a major drawback is represented by the fact that fullereneis not totally protected from the environmental degradation by the waterassociated with the hosts.

F. Lin, S. Mao, Z. Meng and H. Zeng, J. Qiu, Y. Yue and T. Guo in Appl.Phys. Lett., 65 (1994) 2522, described a method for preparing C₆₀fullerene doped phosphate glass by melting in a sealed device. Theproduct obtained in this technique was found to contain in homogeneouslydispersed fullerene clusters.

Recently R. Sahoo, S. K. Bhattacharya and R. Debnath in an Indian Patententitled a novel process for preparing bulk monolith of Carbon sub sixtyfullerene (C₆₀)-glass-composite useful in device applications asnonlinear optical medium and optical limiter”, (No. 622/DEL/2001 datedMay 29, 2001) described a method for preparing bulk monolith offullerene (C₆₀)-glass of different compositions.

According to the above Patent Application, the glass compositioncontains 0-50 mole % phosphorous pentaoxide (P₂O₅), 0-40 mole % boronoxide (B₂O₃), 0-30 mole % bismuth oxide (Bi₂O₃), 0-1 mole % silicondioxide (SiO₂), 0-1 mole % aluminum oxide (Al₂O₃), 10-45.5 mole % zincoxide (ZnO₂), 10-40 mole % lead oxide (PbO), 0-0.1 mole % tin dioxide(SnO₂), 0-5 mole % M₂O where M=Na, K, Li and 0.05-0.10 wt % fullerene(C₆₀).

However, it was noticed that the glass compositions used in this processhave limitations in dissolving fullerene (C₆₀) in a high concentration.The composition described in the aforesaid Indian Patent Application iscapable of keeping fullerene in the medium only in the dispersedcondition. As a result, relatively higher concentration of fullerenenamely fullerene concentration greater than 0.10 wt % cannot beincorporated in the glass composition. As it is preferable toincorporate higher and higher amounts of fullerene in the glasscomposition for device application such as optical limiter andnon-linear media, in the present invention, the aforesaid patentapplication also has some drawbacks.

It is a commonly known principle that effective dissolution of a dopantin a host is achieved only when there occurs some short of interactionbetween the dopant and the host. The compositions disclosed in thepatents in most cases, are not interactive with fullerene (C₆₀),although in some cases they are weakly interactive. Hence the processescan prepare glasses only with low concentration of fullerene.

The main drawbacks of the existing methods of preparation of fullerenedoped glasses are as follows:

-   1) In the case of the fullerene doped sol-gel silica glass,    fullerenes are not totally protected from environmental degradation    as well as from the inherent water molecules associated with the    host.-   2) The sealed device melting method of preparing fullerene-phosphate    glass composite does not yield a homogeneous product and at the same    time suffers from its limitation in offering samples of useful    dimensions.-   3) Fullerene (C₆₀)-glass having high concentration of dissolved    fullerene (C₆₀) can not be achieved using the glass compositions    disclosed so far by the earlier workers. Even, the compositions    recently suggested in the Applicant's earlier Indian Patent    Application No. 622/DEL/2001 dated May 29, 2001 have limitations in    dissolving fullerene (C₆₀) in a high concentration. This is because,    compositions suggested in these earlier studies are in most cases,    either not at all interactive or weakly interactive with fullerene    (C₆₀).

In order to overcome all the above drawbacks, it is essential to providea novel glass composition which is not only capable of dissolving highconcentration of fullerene, but also capable of protecting the fullerenefrom environment degradation. Also, care should be taken to avoidformation of clusters of fullerene during the incorporation.

Keeping in mind all the above-criteria, the Inventors have devised anovel composition which is capable of incorporating 0.15 to 0.20 wt % offullerene in the glass. The synergistic glass composition of the presentinvention is formulated judging the chemical reactivity of theingredients as well as the reactivity of the resulting glass with theincorporated fullerene (C₆₀) to form bonds so that the glass candissolve high concentration of fullerene (C₆₀) in its matrix. TheInventors have noticed that the ingredients and their concentration playa very vital role in overall properties of the glass thus produced. Ifthe ingredients are changed or if the concentrations of the ingredientsare varied beyond the ranges specified in the invention, the propertiesof the glass thus obtained are not satisfactory.

OBJECTS OF THE PRESENT INVENTION

The main object of the present invention is to provide a synergisticcomposition for preparing high concentration fullerene (C₆₀)-glass.

Yet another object of the present invention is to provide a method forpreparing the glass in bulk monolith using the synergistic composition

Still another object of the present invention is to provide a method forpreparing the glass, which is simple and versatile for commercialexploitation.

One more object of the present invention is to provide a fullerene(C₆₀)-glass that is suitable for use as nonlinear photonic material ingeneral and more particularly for various device applications as anefficient nonlinear optical medium, optical limiter.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Accordingly, the present invention provides a synergistic compositionfor preparing high concentration fullerene (C₆₀)-glass useful as anonlinear photonic material in general and particularly in deviceapplications as nonlinear optical medium and optical limiter, whichcomprises: 30-50 mole % of boron oxide (B₂O₃), 10-45 mole % of bismuthoxide (Bi₂O₃), 0 -5 mole % of silicon dioxide (SiO₂), 0-1 mole % ofaluminium oxide (Al₂O₃), 0-30 mole % of zinc oxide (ZnO), 0-45 mole % oflead oxide (PbO) and 0.02-0.20 (wt) % of fullerene C₆₀.

In an embodiment of the present invention the boron oxide used may betaken either as boron oxide itself or as compounds containing boronoxide such as boric acid (H₃BO₃).

In another embodiment of the present invention the bismuth oxide used,may be taken either as it is or as compounds such as bismuth nitrate[Bi(NO₃)₃], bismuth chloride (BiCl₃) or bismuth sub nitrate [OBi(NO₃)].

In yet another embodiment of the present invention the aluminium oxide(Al₂O₃) used, may be taken either as it is or as aluminium hydroxide[Al(OH)₃].

In still another embodiment of the present invention the lead oxide usedmay be taken in the form of lead carbonate (PbCO₃), red lead (Pb₃O₄) orlead fluoride PbF₂.

In one more embodiment of the present invention, the concentration offullerene used is preferably in the range of 0.10 wt % to 0.20 wt % andmore preferably in the range of 0.10 to 0.16 wt %.

Also, the present invention provides a process for preparing glassincorporated with 0.02 to 0.20 wt % of fullerene (C₆₀) in bulk monolith,said process comprising the steps of:

-   (a) heating a mixture comprising of 30-50 mole % of boron oxide    (B₂O₃), 10-45 mole % of bismuth oxide (Bi₂O₃), 0-5 mole % of silicon    dioxide (SiO₂), 0-1 mole % of aluminium oxide (Al₂O₃), 0-30 mole %    of zinc oxide (ZnO) and 0-45 mole % of lead oxide (PbO) at a    temperature in the range of 400-850° C. to obtain a solid mass;-   (b) crushing the solid mass into granules/powders;-   (c) adding 0.02 to 0.20 wt % of fullerene (C₆₀) to the    granules/powder of step (b), mixing the two intimately, heat    treating the mixture at temperature in the range of 350-390° C.    under vacuum and melting the mixture at a temperature in the range    of 600-750° C. under inert gas-atmosphere, and-   (d) cooling the melt of step (c) to obtain a transparent monolithic    glass containing 0.02 to 0.20 wt % of fullerene (C₆₀).

In an embodiment of the present invention the boron oxide used may betaken either as boron oxide itself or as compounds such as boric acid(H₃BO₃).

In another embodiment of the present invention the bismuth oxide used,may be taken either as it is or as compounds such as bismuth nitrate[Bi(NO₃)₃], bismuth chloride (BiCl₃) or bismuth sub nitrate [OBi(NO₃)].

In yet another embodiment of the present invention the aluminium oxide(Al₂O₃) used, may be taken either as it is or as aluminium hydroxide[Al(OH)₃].

In still another embodiment of the present invention the lead oxide usedmay be taken in the form of lead carbonate (PbCO₃), red lead (Pb₃O₄) orlead fluoride PbF₂.

In one more embodiment of the present invention, the concentration offullerene used is preferably in the range of 0.10 wt % to 0.20 wt % andmore preferably in the range of 0.10 to 0.16 wt %.

In one another embodiment of the present invention wherein in step (a),the mixture of boron oxide, bismuth oxide, silicon dioxide, aluminiumoxide, zinc oxide and lead oxide are heated in an alumina crucible.

In a further embodiment of the present invention wherein in step (C),the mixture of fullerene (C₆₀) and the granules is heat-treated in acarbon crucible.

In a further more embodiment of the present invention the inert gasesused may be Helium, Nitrogen, Argon, or mixtures thereof.

The detailed process steps of the present invention are:

-   1. Heating at a temperature in the range 400-850° C. a synergistic    glass composition of 30-50 mole % of boron oxide (B₂O₃), 10-45 mole    % of bismuth oxide (BiO₃), 0-5 mole % of silicon dioxide (SiO₂), 0-1    mole % of aluminium oxide (Al₂O₃), 0-30 mole % of zinc oxide (ZnO),    0-45 mole % of lead oxide (PbO), in an alumina crucible to obtain a    solid mass.-   2. Crushing the sold mass into granules/powder.-   3. Adding fullerene (C₆₀) to the granules/powder in the    concentration range 0.02-0.20 overall wt % of the solid.-   4. Mixing the two components intimately.-   5. Heat treating the mixture in a carbon crucible at a temperature    in the range of 350-390° C. under vacuum.-   6. Melting the mixture at a temperature in the range of 600-750° C.    under inert gas-atmosphere. Cooling the melt to obtain transparent    monolithic glass containing 0.02 to 0.20 wt % of fullerene (C₆₀):

The novel and non-obvious finding of the present invention lies in thefact that the glass composition of the present invention is capable ofdissolving the fullerene, thereby increasing the concentration offullerene getting incorporated. More particularly, the chemicalreactivity of the ingredients as well as the reactivity of the resultingglass with the incorporated fullerene (C₆₀) is such that the glassunexpectedly forms bonds with fullerene due to which the glass candissolve high concentration of fullerene (C₆₀) in its matrix. Theformation of bond not help in increasing the concentration of fullerenegetting incorporated in the glass but also protects the fullerene fromgetting exposed to atmosphere.

Novelty of the present invention lies in selecting a synergisticcomposition for preparing high concentration fullerene (C₆₀)-glass inwhich fullerene (C₆₀) molecules efficiently interact with the host glassand remain homogeneously dispersed in the latter through bonding.

Another novelty of the present invention lies in providing a process forpreparing bulk monolith of the high concentration fullerene (C₆₀)-glassin dimensions suitable for device applications as a nonlinear opticalmedium, optical limiter and in general, as a nonlinear photonicmaterial.

Yet another novel and inventive feature due to which the monolith glasscontaining high concentration of fullerene glass is obtained is the useof two-step method of melting the glass. The two-step process of meltingthe mixture of fullerene (C₆₀) and the granules avoids environmentaldegradation of fullerene (C₆₀) at the time of incorporation of thelatter in the glass. The method provided for preparing bulk monolith ofthe glass using the synergistic composition takes into account thenature of possible interaction of the glass with fullerene (C₆₀),interaction temperature, environment and the time etc.

Also, use of technique of heat treating under vacuum then melting underinert atmosphere in a furnace that can accommodate a batch ranging fromsmall to moderate size.

The following examples provided below are by way of illustrations onlyand should not be construed to limit the scope of the present invention.

EXAMPLE-1

A glass containing high concentration of fullerene was prepared by usingan intimate mixture of 0.28 mole of boric acid (H3BO₃), 0.07 mole ofbismuth oxide (Bi₂O₃), 0.1225 mole of lead carbonate (PbCO₃) and 0.0175mole of SiO₂—heating the batch in an alumina crucible in a furnace at500-600° C. for half an hour—transforming the mass to a clear melt byraising the temperature up to around 800° C.—cooling the melt tosolid—crushing the mass into powder—adding 14 mgm of C₆₀ fullerene to 15gms of the powder—heat treating the mixture in a carbon crucible around360-375° C. for 3 hrs under vacuum—finally melting the mixture at atemperature around 680° C. for 35 minutes under controlled atmosphere ofnitrogen gas. The glass obtained was a monolithic sample having greencolor.

EXAMPLE-2

The fullerene containing glass in an amount 48 gm was also prepared bystarting with a batch mixture of 0.27 mole of H₃BO₃, 0.21 mole ofBi(NO₃)₃, 0.057 mole of PbCO₃ and 0.003 mole of Al₂O₃—melting the batchin an alumina crucible in a furnace at around 650° C.—cooling the moltenmass in the form of lump crushing the same into powder—adding 12 mgm offullerene (C₆₀) to 48 gms of this host material-heat treating themixture in a carbon crucible at 385° C. for 2 hour under vacuum—thenmelting the mixture at 750° C. for 20 mins to a vitreous liquid undercontrolled atmosphere of nitrogen. The glass obtained showed a reddishgreen color.

EXAMPLE-3

In an another trial, the glass was prepared by starting with a batchmixture of 0.1575 mole of B₂O₃, 0.033 mole of ZnO, and 0.315 mole ofOBi(NO₃),—melting the mixture in an alumina crucible by raising thetemperature to around 820° C. in a furnace—cooling the melt to aglass—crushing the lump into frits—adding 10 mgm of (C₆₀) fullerene toabout 6 gms of the frits—heat treating the mixture in a vitreous carboncrucible at around 370° C. for 1 hrs under vacuum—finally melting themixture to a vitreous melt around 700° C. for 0.5 hr under controlledatmosphere of helium gas. The glass obtained was a monolithic samplewith red color.

EXAMPLE-4

Another such glass was prepared by using a batch mixture consisting of0.30 mole H₃BO₃, 0.02 mole of Pb₃O₄, 0.12 mole of BiCl₃ and 0.03 mole ofZnO—melting the batch in a platinum crucible to a sintered mass at atemperature around 700° C.—converting the mass in the form ofgranules—adding 9 mgm of (C₆₀) fullerene to 25 gms the former—mixing thecomponents intimately—heat treating the mixture in a vitreous carboncrucible at around 370° C. for 1 hr under vacuum—then melting themixture by increasing the temperature up to 725° C. for 20 mins. Theglass obtained showed a reddish green color.

EXAMPLE-5

Similar glass was also prepared by using a batch of mixture 0.12 mole ofPbCO₃, 0.294 mole of H₃BO₃ and 0.06 mole of Bi(NO₃)₃ and 0.003 mole ofSiO₂—heat treating the mixture in an alumina crucible at around 550° C.for 5 hour to transform into a sintered mass—crushing the product intopowder—adding 8.5 mgm of C₆₀ fullerene to 30 gms of the powder—mixingthe two components intimately—heat treating the mixture in a carboncrucible at around 390° C. for 1 hr under vacuum—finally melting thesame by raising the temperature to 730° C. for 30 mins under controlledatmosphere of argon to form glass with homogeneous dispersion of C₆₀fullerene. The glass was of green colored.

EXAMPLE-6

A sample of such glass was also prepared by making a batch mixture of0.03 mole of Pb₃O₄, 0.06 mole of Bi(NO₃)₃, 0.30 mole of H₃BO₃, and 0.03mole of ZnO—melting the batch in an alumina crucible at around 700° C.to glassy mass—crushing the glassy mass into frits—adding 12 mgm of C₆₀fullerene to 45 gms of the former—heat treating the new mixture in avitreous carbon crucible at around 380° C. for 1 hr in a closed furnaceunder vacuum—finally melting the material at about 750° C. for 20 minsunder a constant flow of nitrogen. The melt was cooled—the glassobtained had light green color.

Colored transparent monolithic glass samples containing highconcentration fullerene (C₆₀), prepared in different size and shapesusing glass compositions as described above, showed the existence offullerene in the glass mostly as complex and partly as isolatedmolecules, as have been revealed from their color and also from theiroptical absorption study. These are shown in FIG. 1 of the drawingaccompanying the specification. All the samples showed good opticallimiting as well as other nonlinear optical properties.

The main advantages of the invention are:

-   1. The prescribed composition is suitable for dissolving high    concentration of fullerene (C₆₀) in the glass through interactions    between glass and fullerene.-   2. It is superior to our previously disclosed compositions of Indian    patent No. 622/DEL/2001 in respect of efficiency in dissolving    fullerene (C₆₀) in high concentration through interaction with the    latter.-   3. The present method for preparing fullerene (C₆₀) glass can be    used to prepare bulk monolith in dimensions useful in actual device    applications.-   4. The method is superior to sol-gel process both in respect of    homogeneous dispersion and protection of fullerene (C₆₀) from    environmental degradation.-   5. The method is simple and cost effective for commercial    exploitation.

1. A synergistic composition for preparing high concentration fullerene(C₆₀)-glass useful as a nonlinear photonic material in general andparticularly in device applications as nonlinear optical medium andoptical limiter, said composition comprising: 30-50 mole % of boronoxide (B₂O₃), 10-45 mole % of bismuth oxide (Bi₂O₃), 0-5 mole % ofsilicon dioxide (SiO₂), 0-1 mole % of aluminium oxide (Al₂O₃), 0-30 mole% of zinc oxide (ZnO), 0-45 mole % of lead oxide (PbO) and 0.02-0.20(wt) % of fullerene C₆₀.
 2. A synergistic composition as claimed inclaim 1, wherein the boron oxide used may be taken either as it is or ascompounds containing boron oxide such as boric acid (H₃BO₃).
 3. Asynergistic composition as claimed in claim 1, wherein the bismuth oxideused may be taken either as it is or as compounds such as bismuthnitrate [Bi(NO₃)₃], bismuth chloride (BiCl₃) or bismuth sub nitrate[OBi(NO₃)].
 4. A synergistic composition as claimed in claim 1, whereinthe aluminium oxide (Al₂O₃) used may be taken either as it is or asaluminium hydroxide [Al(OH)₃].
 5. A synergistic composition as claimedin claim 1, wherein the lead oxide used may be taken in the form of leadcarbonate (PbCO₃), red lead (Pb₃O₄) or lead fluoride PbF₂.
 6. Asynergistic composition as claimed in claim 1, wherein the concentrationof fullerene used is preferably in the range of 0.10 wt % to 0.20 wt %and more preferably in the range of 0.10 to 0.16 wt %.
 7. A process forpreparing glass incorporated with 0.02 to 0.20 wt % of fullerene (C₆₀)in bulk monolith, said process comprising the steps of: (a) heating amixture comprising of 30-50 mole % of boron oxide (B₂O₃), 10-45 mole %of bismuth oxide (Bi₂O₃), 0-5 mole % of silicon dioxide (SiO₂), 0-1 mole% of aluminium oxide (Al₂O₃), 0-30 mole % of zinc oxide (ZnO) and 0-45mole % of lead oxide (PbO) at a temperature in the range of 400-850° C.to obtain a solid mass; (b) crushing the solid mass intogranules/powders; (c) adding 0.02 to 0.20 wt % of fullerene (C₆₀) to thegranules/powder of step (b), mixing the two intimately, heat treatingthe mixture at temperature in the range of 350-390° C. under vacuum andmelting the mixture at a temperature in the range of 600-750° C. underinert gas-atmosphere, and (d) cooling the melt of step (c) to obtain atransparent monolithic glass containing 0.02 to 0.20 wt % of fullerene(C₆₀).
 8. A process as claimed in claim 7, wherein the boron oxide usedmay be taken either it is or as compounds such as boric acid (H₃BO₃). 9.A process as claimed in claim 7, wherein the bismuth oxide used may betaken either as it is or as compounds such as bismuth nitrate[Bi(NO₃)₃], bismuth chloride (BiCl₃) or bismuth sub nitrate [OBi(NO₃)].10. A process as claimed in claim 7, wherein the aluminium oxide (Al₂O₃)used may be taken either as it is or as aluminium hydroxide [Al(OH)₃].11. A process as claimed in claim 7, wherein the lead oxide used may betaken in the form of lead carbonate (PbCO₃), red lead (Pb₃O₄) or leadfluoride PbF₂.
 12. A process as claimed in claim 7, wherein theconcentration of fullerene used is preferably in the range of 0.10 wt %to 0.20 wt % and more preferably in the range of 0.10 to 0.16 wt %. 13.A process as claimed in claim 7, wherein in step (a), the mixture ofboron oxide, bismuth oxide, silicon dioxide, aluminium oxide, zinc oxideand lead oxide are heated in an alumina crucible.
 14. A process asclaimed in claim 7, wherein in step (C), the mixture of fullerene (C₆₀)and the granules is heat-treated in a carbon crucible.
 15. A process asclaimed in claim 7, wherein the inert gases used may be Helium,Nitrogen, Argon, or a mixture thereof.